KR102628558B1 - adhesive formulation - Google Patents

Abstract

An adhesive composition comprising an epoxy-based adhesive polymer and an elemental phosphorus-containing compound; Method for producing adhesive composition; Methods for increasing the corrosion resistance properties of adhesive compositions; and a method of increasing the corrosion resistance of the substrate by more than 40% by bonding a metal substrate with an adhesive composition.

Description

adhesive formulation

The present invention relates to epoxy-based structural adhesive formulations for joining, for example, metal substrates.

Corrosion resistance or corrosion inhibition is an important property that a metal substrate must exhibit, especially when the metal substrate is exposed to adverse weather conditions. Aluminum (Al) is commonly used in automobile manufacturing in the automotive industry; Typically, during the manufacture of automobiles aluminum metal is bonded to another substrate by an adhesive. In addition to adhesive strength, corrosion resistance (or corrosion inhibition) is an important property that the automotive industry wants to include in structural adhesive formulations. The long service life of vehicles requires adhesives to maintain bonds for many years. During this time, the vehicle and adhesive are exposed to temperature changes as well as water, oil, salt, dirt and other contaminants. These conditions can weaken the adhesive. Adhesive formulations that provide increased corrosion resistance are therefore highly desirable for use in the automotive industry, for example, for bonding metal substrates, such as aluminum, to other metals or other different substrates.

Literature [M. Witten and C.-T. Lin, “Coating Performance of Polyester-Melamine Enamels Catalyzed by an in Situ Phosphatizing Reagent on Aluminum,” Ind. Eng. Chem. Res., vol. 38, pp. 3903-3910, 1999]; and literature [H. Neuder, C. Sizemore, M. Kolody, R. Chiang and C.-T. Lin, “Molecular design of in situ phosphatizing coatings (ISPCs) for aerospace primers,” Progress in Organic Coatings, vol. 47, pp. 225-232, 2003, it is already known in the art that improvements in corrosion resistance and adhesion strength can be obtained for organic coatings on metal substrates when organic or inorganic phosphates are used. In the above references, the term in situ phosphating (ISP) is used to describe the process for increasing the corrosion resistance of coating formulations. This ISP process is also described under the invention title "Additive package for in situ phosphatizing paint, paint and method", registered on June 21, 1994 by C.- T. It is described in U.S. Patent No. 5,322,870 to Lin. All of the above references are incorporated herein by reference. The above references relate to the investigation of in situ phosphating reagents (ISPR) in paints on mild steel. Above M. Witten and C.-T. Lin's literature also shows that the addition of ISPR (e.g. aryl phosphonic acid) to polyester-melamine enamel coatings on aluminum improved adhesion strength compared to controls after salt water immersion tests.

Some patents and academic papers indicate that corrosion resistance can be improved by the use of organic and inorganic phosphates. For example, U.S. Patent No. 5,191,029 describes the use of phosphorus-containing polymer compositions containing water-soluble multivalent metal compounds. The patent states that "(a) a polymer composition comprising one or more polymer(s) containing pendant and/or terminal phosphorus groups....improved solvent resistance, chemical resistance, print resistance, corrosion resistance and “It provides adhesion to metals.”

For example, US Pat. No. 7,297,748 B2 shows that phosphoric acid and organophosphates have some benefit in improving corrosion resistance. The patent describes a direct-to-metal coating containing an acrylic polyol with phosphorylated monomers to improve adhesion and corrosion resistance. The patent describes the use of a two-part approach comprising high monoester polyalkylene oxide acrylate phosphate esters and polyisocyanates.

This is highly desirable to provide a one-component structural epoxy adhesive that strongly bonds metals and other substrates and exhibits good corrosion resistance.

The present invention relates to adhesive compositions that provide increased metal substrate corrosion resistance properties, and methods of increasing the corrosion resistance properties of adhesive compositions, by including low levels of elemental phosphorus-containing (PEC) additives in the adhesive compositions.

One embodiment of the present invention includes (I) an epoxy-based adhesive polymer resin composition; and (II) a PEC compound. In one preferred embodiment, the epoxy-based adhesive polymer is: (a) a curable epoxy compound or a combination of two or more curable epoxy compounds; (b) at least one reactive urethane group- and/or urea group-containing polymer having at least one polyether and/or diene rubber segment having a weight of at least 1,000 atomic mass units and capped isocyanate groups and having a number average molecular weight of at most 35,000, (c) at least one epoxy curing catalyst, and (d) a curing agent.

Another embodiment of the present invention relates to a method for producing the adhesive composition.

Still another embodiment of the invention relates to a method for increasing the corrosion resistance properties of an adhesive composition.

And still another embodiment of the present invention relates to a method of bonding metal substrates with the above structural adhesive composition.

One object of the present invention is to provide an improved product useful for metal adhesives by improving the corrosion resistance of aluminum substrates bonded to epoxy-based structural adhesives without changing the initial product properties of the aluminum or adhesive.

Figure 1 shows the exposed aluminum surface after lap shear testing, including two optical images (row A, top) and four electron micrographs (row B, middle and row C, bottom). This is a series of images of a test sample.
Figure 2 is a series of test samples showing the exposed aluminum surface after lap shear testing, including two optical images (row A, top) and four electron micrographs (row B, middle and row C, bottom). It is an image of .
Figure 3 is a series of electron micrographs showing the polished surface of an aluminum test sample before (left column I) and after treatment with a PEC compound (right column II).

In one general embodiment, the present invention provides a composition comprising: (I) an epoxy-based adhesive polymer resin composition; and (II) an elemental phosphorus-containing compound (PEC).

The epoxy-based adhesive polymer composition useful in the present invention, component (I), includes a curable polymer composition containing one or more of the following components: (a) a curable epoxy compound or a combination of two or more curable epoxy compounds; (b) at least one reactive urethane group- and/or urea group-containing polymer having at least one polyether and/or diene rubber segment having a weight of at least 1,000 atomic mass units and capped isocyanate groups and having a number average molecular weight of at most 35,000, (c) at least one epoxy cure catalyst, and (d) a curing agent.

Epoxy-based adhesive polymer resin compositions useful in the present invention may include curable epoxy compounds, and combinations of two or more curable epoxy compounds. Epoxy resins useful in the present invention include liquids, solids, and combinations thereof. Epoxy compounds include epoxy resins, which may be monomeric (e.g., diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of tetrabromobisphenol A, novolak-based epoxy resins, and tris -epoxy resin); Higher molecular weight resins (such as diglycidyl ether of bisphenol A promoted with bisphenol A); or unsaturated monoepoxides polymerized into homopolymers or copolymers (e.g., glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, etc.). Epoxy compounds contain, on average, at least one pendant or terminal 1,2-epoxy group (i.e., adjacent epoxy group) per molecule. Solid epoxy resins that can be used in the present invention are mainly based on bisphenol A. Preferred solid epoxy resins useful in the present invention include D.E.R. commercially available from Olin Corporation. Diglycidyl ethers of bisphenol A, such as 664 UE solid epoxy, may be included. Other suitable epoxy resins useful in the present invention include, for example, D.E.R., all commercially available from Olin. 331, D.E.R. 332, D.E.R. 383, D.E.R. 431 and D.E.R.736 may be included.

The adhesive contains component (a), at least one epoxy resin that is non-rubber-modified and non-phosphorus-modified. “Non-rubber-modified” means that the epoxy resin is not chemically bonded to the rubber prior to curing, as described below. “Non-phosphorus-modified” means that before curing the adhesive, the epoxy resin has not reacted with phosphoric acid, polyphosphoric acid, phosphoric acid or polyphosphoric acid salt, or phosphoric acid or polyphosphoric acid ester, so that it contains one or more moieties having the structure: moiety) is not introduced into the resin structure:

If only a single non-rubber-modified, non-phosphorus-modified epoxy resin is present, the epoxy resin is liquid at 23 degrees Celsius (°C). When two or more non-rubber-modified, non-phosphorus-modified epoxy resins are present, their mixture is liquid at 23°C, but the individual epoxy resins in the mixture may themselves be solid at 23°C.

A wide range of epoxy resins can be used as non-rubber-modified, non-phosphorus-modified epoxy resins, including those described in U.S. Pat. No. 4,734,332, column 2, line 66 to column 4, line 24, which is incorporated herein by reference. The epoxy resin should have an average of 1.8 or more epoxide groups per molecule, preferably 2.0 or more. The epoxy equivalent weight may be, for example, 75 to 350, 140 to 250, and/or 150 to 225. If a mixture of non-rubber-modified, non-phosphorus-modified epoxy resins is present, the mixture should have an average epoxy functionality of at least 1.8, preferably at least 2.0 and an epoxy equivalent weight as in the previous sentence, more preferably Each epoxy resin in the mixture has such an epoxy functionality and epoxy equivalent weight.

Suitable non-rubber-modified, non-phosphorus-modified epoxy resins useful in the present invention include resorcinol, catechol, hydroquinone, biphenol, bisphenol A, bisphenol AP (1,1-bis (4-hydroxyl diglycidyl ethers of polyhydric phenol compounds such as phenyl)-1-phenyl ethane), bisphenol F, bisphenol K and tetramethylbiphenol; diglycidyl ethers of aliphatic glycols, such as diglycidyl ethers of C _2-24 alkylene glycols; Phenol-formaldehyde novolak resin (epoxy novolak resin), alkyl substituted phenol-formaldehyde resin, phenol-hydroxybenzaldehyde resin, cresol-hydroxybenzaldehyde resin, dicyclopentadiene-phenol resin and dicyclopentadiene-substituted polyglycidyl ether of phenolic resin; and any combination of any two or more of these.

Suitable epoxy resins useful in the present invention include diglycidyl ethers of bisphenol A resins, such as those sold by Olin Corporation under the trade names ^DER® 330, DER 331, DER 332, DER 383, DER 661 and DER 662 resins.

Epoxy novolac resins can also be used in the present invention. Such epoxy novolac resins include, for example, ^DEN® 354, DEN 431, DEN 438 and DEN 439, available commercially from Olin Corporation.

Other suitable non-rubber-modified, non-phosphorus-modified epoxy resins useful in the present invention are cycloaliphatic epoxides. Cycloaliphatic epoxides contain a saturated carbon ring with an epoxy oxygen (O) bonded to two adjacent atoms within the carbon ring, as illustrated in the structure below:

Here, R is an aliphatic, cycloaliphatic and/or aromatic group and n is a number from 1 to 10, preferably from 2 to 4. When n is 1, the cycloaliphatic epoxide is a monoepoxide. When n is 2 or more, diepoxide or polyepoxide is formed. Mixtures of monoepoxides, diepoxides and/or polyepoxides may be used. Cycloaliphatic epoxy resins as described in U.S. Pat. No. 3,686,359, which is incorporated herein by reference, may be used in the present invention. In particular, cycloaliphatic epoxy resins of interest include (3,4-epoxycyclohexyl-methyl)-3,4-epoxy-cyclohexane carboxylate, bis-(3,4-epoxycyclohexyl) adipate, and vinylcyclohexyl. Hexene monoxide and mixtures thereof.

Other suitable epoxy resins useful in the present invention include oxazolidone-containing compounds as described in U.S. Pat. No. 5,112,932. Additionally, D.E.R. 592 and D.E.R. Enhanced epoxy-isocyanate copolymers, such as those sold commercially as 6508, can be used.

In some embodiments, the non-rubber-modified, non-phosphorus-modified epoxy resin is a first diglycidyl bisphenol ether having an epoxy equivalent weight of up to 225 and a second diglycidyl bisphenol ether having an epoxy equivalent weight of from 225 to greater than 750. Contains cidyl bisphenol ether. The first diglycidyl bisphenol ether itself may be liquid at 23° C. and the second diglycidyl bisphenol ether may be solid at 23° C., provided that the mixture is liquid at that temperature. Each of these can be the diglycidyl ether of bisphenol-A or bisphenol-F, which can be partially promoted to obtain epoxy equivalents as indicated.

Component (a) may constitute at least 20 weight percent, at least 30 weight percent, or at least 40 weight percent of the total weight of the adhesive, and up to 80 weight percent, at most 70 weight percent, or at most It may constitute 60% by weight.

Component (b) is one or more reactive urethane group- and/or urea group-containing polymers having at least one polyether or diene rubber segment having a weight of at least 1,000 atomic mass units and capped isocyanate groups and having a number average molecular weight of at most 35,000. . Such materials are described, for example, in US Patent No. 5,202,390, US Patent No. 5,278,257, International Publication No. WO 2005/118734, International Publication WO 2007/003650, International Publication WO 2012/091842, US Patent Application Publication No. 2005/0070634. Ho, US Patent Application Publication No. 2005/0209401, US Patent Application Publication No. 2006/0276601, EP-A-0 308 664, EP 1 498 441A, EP-A 1 728 825, EP-A 1 896 517, EP-A 1 916 269, EP-A 1 916 270, EP-A 1 916 272 and EP-A-1 916 285, all of which are incorporated herein by reference.

Component (b) materials are conveniently prepared in a process comprising forming an isocyanate-terminated polyether and/or diene rubber and capping the isocyanate groups with phenol or polyphenol. Isocyanate-terminated polyether and/or diene rubbers are prepared by reacting a hydroxyl- or amine-terminated polyether, a hydroxyl- or amine-terminated diene rubber, or a mixture of both with an excess of polyisocyanate to form a urethane or urea. It is conveniently prepared by producing an adduct with a group and a terminal isocyanate group. If desired, the isocyanate-terminated polyether or diene rubber can be chain-extended and/or branched simultaneously with or prior to performing the capping reaction.

Isocyanate-terminated polyether and isocyanate-terminated diene polymers can have aromatic or aliphatic isocyanate groups. The polyisocyanate used to prepare this material preferably has at least two isocyanate groups per molecule and has a molecular weight of up to 300 grams per mole (g/mol). The polyisocyanate may be an aliphatic polyisocyanate, such as toluene diamine or aromatic polyisocyanate such as 2,4'- and/or 4,4'-diphenylmethane diamine, or isophorone diisocyanate, 1,6-hexamethylene diamine It may be isocyanate, hydrogenated toluene diisocyanate, or hydrogenated methylene diphenyl isocyanate (H ₁₂ MDI).

Hydroxyl- or amine-terminated polyethers include tetrahydrofuran (tetramethylene oxide), 1,2-butylene oxide, 2,3-butylene oxide, 1,2-propylene oxide, and ethylene oxide. It may be one or more polymers or copolymers, and may contain at least 70% of tetrahydrofuran, 1,2-butylene oxide, 2,3-butylene oxide, and 1,2-butylene oxide, based on the total weight of the polymer or copolymer. Polymers or copolymers of propylene oxide are preferred. Particular preference is given to polymers of at least 80% by weight of tetrahydrofuran, based on the total weight of the polymer or copolymer. The starting polyether preferably has 2 to 3, more preferably 2 hydroxyl and/or primary or secondary amino groups per molecule. The starting polyether preferably has a number average molecular weight of 900 to 8,000, more preferably 1,500 to 6,000, or 1,500 to 4,000.

The hydroxyl- or amine-terminated diene polymer preferably has a glass transition temperature of -20°C or lower, preferably -40°C or lower, before reaction with the polyisocyanate. Diene polymers are liquid homopolymers or copolymers of conjugated dienes, especially diene/nitrile copolymers. The conjugated diene is preferably butadiene or isoprene, with butadiene being particularly preferred. The preferred nitrile monomer is acrylonitrile. A preferred copolymer is butadiene-acrylonitrile copolymer. The rubber preferably contains in the agglomerate not more than 30% by weight of polymerized unsaturated nitrile monomers, preferably not more than 26% by weight of polymerized nitrile monomers. The hydroxyl- or amine-terminated diene polymer preferably has 1.8 to 4, more preferably 2 to 3 hydroxyl and/or primary or secondary amino groups per molecule. The starting diene polymer preferably has a number average molecular weight of 900 to 8,000, more preferably 1,500 to 6,000, and even more preferably 2,000 to 3,000.

Isocyanate-terminated polymers are made by combining the above-described polyisocyanates with hydroxyl- or amine-terminated polyethers and/or hydroxyl- or amine-terminated diene rubbers by hydroxyl and/or primary on the starting polyether or diene rubber. or at least 1.5 equivalents per equivalent of secondary amino group, preferably 1.8 equivalents to 2.5 equivalents or 1.9 equivalents to 2.2 equivalents of polyisocyanate.

The reaction to form the isocyanate-terminated polymer involves combining the starting polyether and/or diene rubber with a polyisocyanate, optionally in the presence of a catalyst for reaction of the isocyanate groups with the isocyanate-reactive groups of the polyether or diene polymer. This can be done by heating from 60°C to 120°C. The reaction continues until the isocyanate content is reduced to a constant or target value, or until the amino- and/or hydroxyl groups of the starting polyether or diene polymer are consumed.

If desired, branching can be effected by adding a branching agent to the reaction between the starting polyether or diene polymer and the polyisocyanate, or in a subsequent step. For the purposes of the present invention, branching agents are polyols or polyamine compounds having a molecular weight of at most 599, preferably 50 to 500, and at least 3 hydroxyl, primary amino and/or secondary amino groups per molecule. If used, the branching agent generally constitutes not more than 10% by weight, preferably not more than 5% by weight, and even more preferably not more than 2% by weight of the combined weight of the branching agent and the starting polyether or diene polymer. Examples of branching agents useful in the present invention include trimethylolpropane, glycerin, trimethylolethane, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, sucrose, sorbitol, pentaerythritol, triethanolamine, diethanolamine, etc. As well as polyols, their alkoxylates having a number average molecular weight of up to 599, especially up to 500, are included.

If desired, i) by including a chain extender in the reaction to form the isocyanate-terminated polyether and/or diene polymer, or ii) before or during the capping step. Chain extension can be accomplished by reacting the polymer with a chain extender. Chain extenders useful in the present invention include polyol or polyamine compounds having a molecular weight of up to 749, preferably 50 to 500, and two hydroxyl, primary amino and/or secondary amino groups per molecule. Examples of suitable chain extenders useful in the present invention include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol, 1,6-hexane diol, cyclohexanediol. aliphatic diols such as methanol; aliphatic or aromatic diamines such as ethylene diamine, piperazine, aminoethylpiperazine, phenylene diamine, diethyltoluenediamine, etc.; and resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (1,1-bis(4-hydroxylphenyl)-1-phenyl ethane), bisphenol F, bisphenol K, bisphenol M, tetramethylbiphenol. and compounds having two phenolic hydroxyl groups such as o,o'-diallyl-bisphenol A. Among these, compounds having two phenolic hydroxyl groups are preferable.

The isocyanate groups of the isocyanate-terminated polyether or diene polymer are capped by reaction with a capping agent. Suitable capping agents useful in the present invention are described, for example, in International Publication No. WO 2017/044359, incorporated herein by reference, and include various mono- and polyphenolic compounds, as well as various amines, as further described below. compounds, benzyl alcohol, hydroxy-functional acrylate or methacrylate compounds, thiol compounds, alkyl amide compounds with at least one amine hydrogen such as acetamide, and ketoxime compounds.

In some embodiments, at least 90 percent (%) of the isocyanate groups are capped with a monophenol or polyphenol. Examples of monophenols useful in the present invention include phenols, alkyl phenols containing one or more alkyl groups that can each contain from 1 carbon atom to 30 carbon atoms, halogenated phenols, cardanol, or naphthol. Suitable polyphenols useful in the present invention contain at least 2, preferably 2 phenolic hydroxyl groups per molecule and include resorcinol, catechol, hydroquinone, biphenol, bisphenol A, bisphenol AP (1,1-bis( 4-hydroxylphenyl)-1-phenyl ethane), bisphenol F, bisphenol K, bisphenol M, tetramethylbiphenol and o,o'-diallyl-bisphenol A as well as their halogenated derivatives. In such an embodiment, up to 10%, preferably up to 5%, of the isocyanate groups may be capped with a capping agent as mentioned above.

The capping reaction is carried out under the general conditions already described, i.e. combining the materials in the ratios mentioned and optionally in the presence of a catalyst for the reaction of the isocyanate groups with the isocyanate-reactive groups of the capping agent, at an elevated temperature such as from 60° C. to 120° C. or at room temperature. It can be performed by reacting in . The reaction continues until the isocyanate content is reduced to a constant value, preferably less than 0.1% by weight. Less than 3%, preferably less than 1%, of the isocyanate groups may remain uncapped.

The capping reaction can be performed simultaneously with the isocyanate-terminated polyether and/or diene polymer being formed, or as a separate capping step.

The resulting component (b) material suitably has a number average molecular weight as measured by GPC of at least 3,000, preferably from at least 4,000 to about 35,000, preferably about 20,000, considering only peaks representing molecular weights of 1,000 or more. , and more preferably up to about 15,000.

The polydispersity (ratio of weight average molecular weight to number average molecular weight) of component (b) is suitably from about 1 to about 4, preferably from about 1.5 to 2.5.

Component (b) may constitute at least 0.5%, at least 2%, at least 5%, at least 10% or at least 15% by weight of the total weight of the adhesive, up to 40% by weight of the total weight of the adhesive, It may constitute up to 30% by weight or up to 25% by weight.

Epoxy curing catalyst, component (c), is one or more materials that catalyze the reaction of the epoxy resin(s) with the curing agent. Epoxy cure catalysts useful in the present invention are preferably encapsulated or otherwise of the latent type, becoming active only upon exposure to elevated temperatures. Preferred epoxy catalysts useful in the present invention are in particular p-chlorophenyl-N,N-dimethylurea (monuron), 3-phenyl-1,1-dimethylurea (phenouron), 3,4-dichlorophenyl-N,N -Ureas such as dimethylurea (diuron), N-(3-chloro-4-methylphenyl)-N',N'-dimethylurea (chlortoluron), benzyldimethylamine, 2,4,6-tris(dimethyl tert-acrylic- or alkylene amines such as aminomethyl)phenol, piperidine or their derivatives, various aliphatic urea compounds as described in EP 1 916 272; C ₁ -C ₁₂ alkylene imidazole, such as 2-ethyl-2-methylimidazole, or N-butylimidazole, and 6-caprolactam. 2,4,6-tris(dimethylaminomethyl)phenol incorporated in a poly(p-vinylphenol) matrix (as described in European Patent EP 0 197 892), or those described in US Pat. No. 4,701,378, 2,4,6-tris(dimethylaminomethyl)phenol incorporated in novolac resin is suitable.

Component (c) may constitute at least 0.1% by weight, at least 0.25% by weight, or at least 0.5% by weight of the total weight of components (a) through (d), for example, ) may constitute up to 5% by weight, up to 3% by weight or up to 2% by weight of the total weight of.

The curing agent useful in the present invention, component (d), is selected together with component (c) such that the adhesive exhibits a cure temperature of at least 60°C. The curing temperature is preferably 80°C or higher, and may be 100°C or higher, 120°C or higher, 130°C or higher, or 140°C or higher. The curing temperature may be as high as 180° C., for example. “Cure temperature” herein refers to the lowest temperature at which a structural adhesive achieves at least 30% of the lap shear strength (DIN ISO 1465) of the adhesive at full cure within 2 hours. The lap shear strength at “full cure” is measured for samples cured at 180° C. for 30 minutes (min), these conditions representing “full cure” conditions. A clean (degreased) 1.2 millimeter (mm) HC420LAD+Z100 galvanized steel substrate, a bonding area of 10 x 25 mm and an adhesive layer thickness of 0.3 mm are suitable parameters to perform the evaluation.

The curing agent, component (d), is a compound that reacts with at least two epoxy groups to form a linkage between them. Suitable curing agents useful in the present invention include boron trichloride/amine and boron trifluoride/amine complexes, dicyandiamide, melamine, diallylmelamine, dicyandiamide, methyl guanidine, dimethyl guanidine, trimethyl guanidine, tetramethyl guanidine, methylisobi. Guanamines such as guanidine, dimethylisobiguanidine, tetramethylisobiguanidine, heptamethylisobiguanidine, hexamethylisobiguanidine, acetoguanamine and benzoguanamine, 3-amino-1,2,4-triazole and hydrazides such as aminotriazole, adipic acid dihydrazide, stearic acid dihydrazide, isophthalic acid dihydrazide, semicarbazide, cyanoacetamide, and aromatic polyamines such as diaminodiphenylsulfone. Materials are included. Particularly preferred for use in the present invention are dicyandiamide, isophthalic dihydrazide, adipic acid dihydrazide and/or 4,4'-diaminodiphenylsulfone.

Component (d) is present in an amount sufficient to cure the composition. Typically, sufficient curing agent is provided to consume at least 80% of the epoxide groups present in the composition. Excesses exceeding those required to fully consume the epoxide groups are generally not necessary. Preferably, the curing agent makes up at least about 1.5% by weight of the adhesive, more preferably at least about 2.5% and even more preferably at least 3.0% by weight. The curing agent may preferably comprise up to about 15% by weight of the adhesive, up to about 10% by weight of the adhesive, up to about 8% by weight of the adhesive, up to about 7% by weight of the adhesive, or up to about 5% by weight of the adhesive.

The weight of components (a) to (d) may be, for example, 30% to 100%, 50% to 100%, 50% to 90% or 50% to 85% by weight of the total weight of the adhesive. Weight percent can be configured. If components (a) to (d) constitute less than 100% of the total weight of the adhesive, the adhesive may also contain one or more optional components.

The adhesives of the present invention include fillers, tackifiers, toughening agents, flexibilizers, curing catalysts, stabilizing catalysts, color additives, dimerizing fatty acids, reactive and/or non-reactive diluents, pigments and dyes, It may additionally contain optional ingredients such as flame retardants, thixotropic agents, swelling agents, flow control agents, adhesion promoters, antioxidants, viscosity modifiers, solvents, corrosion protectants and glass beads. Suitable bulking agents include both physical and chemical types of agents. The adhesive may also contain thermoplastic powders such as polyvinylbutyral or polyester polyols as described in International Publication No. WO2005/118734. Suitable optional ingredients useful in adhesive formulations may include both physical and chemical types of agents. For example, ingredients can be used to make the material wash off resistant, or to allow the formulation to cure at low temperatures.

For example, the adhesive formulations of the present invention may contain one or more particulate fillers. The filler is solid at the temperature reached in the curing reaction. These fillers have the ability to (1) control the fluidity of the adhesive in a desirable manner, (2) reduce the overall cost per unit weight, and (3) absorb moisture or oil from the adhesive or from the substrate to which the adhesive is applied. , and/or (4) induce cohesive failure rather than adhesive failure. Examples of suitable mineral fillers include calcium carbonate, calcium oxide, talc, carbon black, textile fibers, glass particles or fibers, aramid pulp, boron fibers, carbon fibers, mineral silicates, mica, powdered quartz, hydrated aluminum oxide, bentonite, wollastonite. , kaolin, fumed silica, silica airgel, polyurea compounds, polyamide compounds, metal powders such as aluminum powder or iron powder, and expandable microballoons. Mixtures of fillers may be used, comprising at least fumed silica and calcium oxide and may further comprise calcium carbonate, kaolin and/or wollastonite. Particulate fillers may, for example, make up at least 5%, at least 10%, or at least 12% by weight of the total weight of the adhesive; It may constitute the top 35%, up to 30%, up to 25% or up to 20% by weight of the total weight of the adhesive. If the mineral filler comprises fumed silica, the adhesive may contain up to 10% by weight fumed silica, preferably between 1% and 6% by weight.

All or part of the mineral filler may be in the form of fibers with a diameter (D50, as measured microscopically) of 1 μm to 50 μm and an aspect ratio of 6 to 20. The diameter of the fiber may be 2 to 30 μm or 2 to 16 μm and the aspect ratio may be 8 to 40 or 8 to 20. The diameter of the fiber is taken as the diameter of a circle with the same cross-sectional area as the fiber. The aspect ratio of the fibers may be greater than or equal to 6, such as 6 to 40, 6 to 25, 8 to 20, or 8 to 15.

Alternatively, all or part of the mineral filler may be in the form of low aspect ratio particles with an aspect ratio of less than 5, especially less than 2, and a longest dimension of at most 100 μm, preferably at most 25 μm.

One of the advantages of using epoxy resins in the present invention is the ability to provide a toughened adhesive for structural bonding. The adhesive is advantageously a low viscosity resin at room temperature so that the adhesive can be applied at room temperature. For example, toughening systems used as structural adhesives include aliphatic urethane polymer P92-500, polyurethane adduct P99-0151, polyurethane adduct P15-0346, polyurethane adduct EUP27 (P10-0078), aliphatic Urethane polymer P16-0227 and/or butadiene-acrylic copolymer are included. The viscosity at 25° C. of the room temperature pumpable adhesive generally ranges from about 400 Pascal-second (Pa.s) to about 4,000 Pa.s in one embodiment, as measured via a rheometer at a shear rate of 3 1/s; in another embodiment from about 600 Pa.s to about 2,500 Pa.s; and still another embodiment from about 800 Pa.s to about 1,500 Pa.s.

In another embodiment, among the optional ingredients useful in the present invention are one or more rubbers. The at least one rubber comprises, for example, a rubber-modified epoxy resin different from component (a), i.e. having at least two epoxide groups separated by an aliphatic chain of at least 300 g/mol, preferably at least 500 g/mol. Compounds are included. Aliphatic chains include, for example, alkylene groups; alkenyl group; diene polymer or copolymer; or it may be a polyether such as poly(propylene oxide), poly(ethylene oxide), or a copolymer of propylene oxide and ethylene oxide. Other rubber-modified epoxy resins useful in the present invention include epoxidized fatty acids (which may be dimerized or oligomerized), and elastomeric polyesters modified to contain epoxy groups. The rubber-modified epoxy resin, before curing, may have a glass transition temperature of -20°C or lower, preferably -30°C or lower.

The optional rubber may include core-shell rubber particles, provided that, if present, the core-shell rubber particles constitute up to 7% by weight of the total weight of the adhesive. Preferably the core-shell rubber constitutes no more than 5%, no more than 2.5%, or no more than 1% of the total weight of the adhesive and may be absent from the adhesive.

Glass microballoons having an average particle size of up to 200 micrometers and a density of up to 0.4 grams per cubic centimeter (g/cc) may be present in the adhesive of the present invention. If present, glass microballoons may be used in an amount of at most 5% by weight of the total weight of the adhesive, and more preferably at most 2% by weight or at most 1% by weight of the total weight of the adhesive. Suitable microballoons useful in the present invention include ^3M® Glass Bubbles K25 from 3M Corporation. Accordingly, in some embodiments, the glass microballoons may be absent and present in an amount of up to 0.5% or up to 0.25% by weight of the total weight of the adhesive.

In other embodiments, monomeric or oligomeric, addition polymerizable, ethylenically unsaturated materials are optionally present in the adhesive composition. This material may have a molecular weight of less than about 1500. This material may be, for example, an acrylate or methacrylate compound, an unsaturated polyester, a vinyl ester resin, or an epoxy adduct of an unsaturated polyester resin. A free radical initiator may also be included in the adhesive composition to provide a source of free radicals for polymerizing this material. The inclusion of this type of ethylenically unsaturated material in the adhesive composition offers the possibility of achieving partial curing of the adhesive through selective polymerization of the ethylenically unsaturated body.

The epoxy-based resin polymer composition, component (I), is preferably prepared by mixing the above-mentioned components together before adding the PEC compound, component (II). Alternatively, the PEC compound, component (II), can be mixed with components (a) through (d) to form the adhesive of the present invention.

In one embodiment, the epoxy-based resin polymer composition that can be used as component (I) in the present invention is provided as a separate component before adding the PEC compound. In this embodiment, the epoxy-based resin polymer composition may include a number of epoxy-based resin polymer compositions sold under the trade name BETAMATE ^® and commercially available from The Dow Chemical Company. Some of the specific BETAMATE products useful in the present invention may include, for example, BETAMATE 1620US, BETAMATE 1480V203, BETAMATE 1486, BETAMATE 1489HM, BETAMATE 4601, BETAMATE 6160, BETAMATE 1630US, and BETAMATE 1640US.

The concentration of the epoxy-based resin polymer composition used in the adhesive formulation is, in one embodiment, from about 30% to about 70% by weight, based on BETAMATE 1620 US; in another embodiment from about 40% to about 65% by weight; and in yet another embodiment it may range from about 45% to about 60% by weight.

PEC compounds useful in the present invention may include, for example, organic and inorganic species. In a preferred embodiment, the phosphorus element in the PEC compound is bonded to 1 to 4 oxygen atoms. Representative PEC compounds useful in the present invention include orthophosphoric acid; polyphosphoric acid/polyphosphonic acid; derived conjugate bases including phosphate and phosphite; and one or more polymer(s) containing pendant and/or terminal phosphorus groups with phosphorus containing monomers including, for example, phosphoethylmethacrylate, phospho-di(ethyl methacrylate), and allyl phosphate. A polymer composition may be included.

The concentration of the PEC compound in the adhesive formulation is, in one embodiment, from about 0.01% to about 10% by weight; in another embodiment from about 0.1% to about 5% by weight; and in yet another embodiment it may range from about 0.1% to about 3% by weight.

The method for producing the adhesive composition of the present invention includes mixing the epoxy-based adhesive polymer described above, component (I) and the PEC compound described above, component (II) at room temperature and at 55° C. or lower, more preferably at 50° C. or lower. It includes steps to: The resulting adhesive is a one-part adhesive in which the above-mentioned ingredients are mixed together before application and curing. The way the ingredients are combined is not particularly important, as long as the temperature is low enough that premature curing does not occur. It is important to control the mixing temperature because excessive heat can adversely affect the shelf life of the product. Additionally, the order of addition is preferably carried out to produce a stable product. For example, in one embodiment, the ingredients are added and adjusted early. In another embodiment, ingredients are added later to minimize heat history. For short-term exposure to facilitate bulk application, the maximum temperature at which the ingredients are mixed together may be increased up to 55°C.

The formulated adhesive may be stored at a temperature of, for example, up to 100°C, up to 80°C, up to 60°C, or up to 40°C for a period of at least 1 day before the adhesive is applied and cured.

The resulting adhesive composition product of the present invention produced by the above process is a homogeneous liquid blend of components. The adhesive product is stable at ambient conditions; It can be easily applied to a substrate. “Stable” means that the adhesive product is fluid at ambient conditions and generally has a viscosity of less than about 1500 Pa.s; The individual ingredients are inert, meaning that when mixed together they do not react with each other to give unwanted byproducts.

Once the formulation of the present invention has been prepared as described above, the formulation can be used in a variety of applications. In one broad embodiment of the invention, the formulation can be used as an adhesive to join two substrates. For example, in one embodiment, the adhesive composition described above may form a layer at a bondline between two substrates to form an assembly, and the adhesive layer cures at the bondline to form an assembly of each of the two substrates. Forms a cured adhesive bonded to the.

The adhesive of the present invention may be applied to the substrate by any convenient technique. For example, the adhesive formulation of the present invention can be applied to at least a portion of the surface of the substrate by brushing, calendaring, spraying, dipping, rolling or other conventional means. If necessary, the adhesive may be applied cold or hot. The adhesive may be applied manually and/or robotically, for example using a caulking gun, other extrusion device, or jet spraying methods. Once the adhesive composition is applied to the surface of at least one of the substrates, the substrates are brought into contact such that the adhesive is positioned at the bonding surface between the substrates.

After application, the adhesive is cured by heating the adhesive to or above its curing temperature. It is generally preferred to carry out the curing step by heating the adhesive to 130° C. or higher, although in some cases, particularly where longer curing times can be tolerated, lower temperatures may be used. The heating temperature can be as high as 220°C or higher, but since the advantage of the present invention is a lower cure onset temperature, the curing temperature is preferably at most 200°C, at most 180°C, at most 170°C or at most 165°C.

Adhesives of the present invention can be used on a variety of adhesives, including, for example, wood, metal, coated metal, steel, metal such as zinc, copper, bronze, magnesium, titanium and/or aluminum, various plastic and filled plastic substrates, fiberglass, etc. It can be used to bond substrates together.

The substrates may be different materials. Examples of substrate combinations include combinations of different metals such as steel and aluminum, steel and magnesium, and aluminum and magnesium; Combinations of metals such as steel, magnesium, aluminum or titanium with polymeric materials such as thermoplastic or thermosetting organic polymers; and combinations of metals such as steel aluminum, magnesium or titanium with fiber composites such as carbon fiber composites or glass fiber composites.

In one preferred embodiment, the adhesive formulation of the present invention is used for bonding same or different metal substrates together; Alternatively, it may be advantageously used to bond metals to other substrates such as thermoplastics, thermosets, reinforced plastics, or glass. Methods for bonding substrates include, for example, (A) (I) an epoxy-based adhesive polymer; and (II) mixing the PEC compound to form a structural adhesive formulation; (B) After contacting the formulation from step (A) with at least a portion of the surface of the first substrate, the first substrate is brought into contact with another second substrate to form a process of step (A) at the joint surface between the two substrates. forming a layer of adhesive (the layer in step (B) has a thickness of 0.1 mm to 3 mm and may contain a solid spacer such as a glass bead to maintain the thickness); (C) contacting the first substrate and the second substrate through a layer of adhesive formulation at the joint surface between the two substrates to form an assembly; and (D) curing the adhesive layer at the bonding surface by heating it to a temperature of 130° C. or higher to form a cured adhesive bonded to the two substrates at the bonding surface; The lap shear strength of the adhesive formulation of the present invention after 500 hours of exposure to 35° C. and 5% NaCl salt spray (ASTM B117-16) increases by more than about 30 times.

The formulation of the present invention can be used as an adhesive to bond a first substrate to a second substrate. The first substrate and the second substrate may be different substrates or the first substrate and the second substrate may be the same substrate. In one embodiment, the first substrate is selected from metals such as aluminum, and iron-based metals such as carbon steel. In a preferred embodiment, the first metal substrate is aluminum.

The second substrate may be selected from various types of substrates, including, for example, metals such as aluminum and steel, glass, fabric, metal, rubber, and composite materials. In a preferred embodiment, the second substrate is another metal, such as aluminum metal.

In one preferred embodiment, the adhesive is used to join parts of an automobile together or to join an automobile component to an automobile. A particularly targeted application is the joining of automobile or other vehicle frame components to each other or to other components. Assembled automobile and other vehicle frame members are usually coated with coating materials that require bake hardening. Coatings are typically baked at temperatures that can range from 160°C to 210°C. In such cases, it is often convenient to apply the adhesive to the framing component, then apply the coating, bake and cure the coating, and allow the adhesive to cure at the same time. Between applying the adhesive and applying the coating, the assembly may be fastened together to maintain the substrate and adhesive in a fixed position relative to each other until the curing step is performed. Mechanical means may be used as fastening devices. Fastening devices include, for example, temporary mechanical means such as various types of clamps, bands, etc., which can be removed once the curing step is complete. The mechanical fastening means may be permanent, for example various types of welding, rivets, screws and/or crimping methods. Alternatively or additionally, fastening may include spot-curing one or more specific portions of the adhesive composition to form one or more localized adhesive bonds between the substrates while leaving the remainder of the adhesive to undergo a final curing step after the coating has been applied. This can be accomplished by remaining uncured until

The resulting benefits of the adhesive formulations of the present invention include, for example: (1) increased corrosion resistance to metal substrates, such as aluminum substrates bonded to epoxy-based structural adhesives; (2) maintenance of the bonding strength of the adhesive; and (3) a reduction in the failure mode after cycling of the adhesive.

The cured adhesive may have a Casson plastic viscosity of greater than 25 Pascals (Pa), greater than 50 Pa, or greater than 70 Pa, up to 1,000 Pa, up to 700 Pa, up to 400 Pa, or up to 200 Pa at 45°C.

Especially when the adhesive is used as a structural adhesive, the stronger the corrosion resistance properties that the adhesive exhibits, the better. Improved performance in terms of corrosion resistance can be observed as an improvement in the lap shear performance of the bonded metal substrates (bonded together by the adhesive of the present invention) after exposure to accelerated corrosion conditions outlined in ASTM B117-16. For example, lap shear strength can be measured in megapascals (MPa) for an epoxy-based adhesive after a 500 hour salt spray test using a 5% NaCl solution by weight at 35°C.

In general, the corrosion resistance properties of adhesive formulations containing the PEC additives of the present invention can be increased from the original corrosion resistance properties of adhesives without PEC additives. The corrosion resistance properties of the adhesive formulation without PEC additives are approximately 0.4 MPa. Generally, the corrosion resistance properties, lap shear strength, of the adhesive formulations of the present invention are about 32 times higher than 0.4 MPa in one embodiment, about 31 times higher than 0.4 MPa in another embodiment, and in another embodiment. It can be measured to be about 30 times higher than 0.4 MPa. In other embodiments, the corrosion resistance properties of the adhesive formulation can range from about 18 times higher than 0.4 MPa to about 30 times higher than 0.4 MPa.

As mentioned above, a particular advantage of the present invention is that the adhesive has excellent resistance to corrosion aging; For the purposes of this invention, corrosion resistance is evaluated by the lap shear strength test according to ASTM B117-16. Test samples are prepared as described in the Examples below. The lap shear strength of the unaged test sample is measured. The same test samples are prepared and exposed to 90 cycles of the Volkswagen PV 1210 corrosion aging protocol and the lap shear strength of the samples is measured. Adhesives of the present invention often exhibit a loss of up to 40% of lap shear strength after the corrosion protocol compared to the lap shear strength of unaged samples. In some embodiments, this excellent resistance to corrosion aging is achieved when the adhesive contains very low amounts of glass microspheres (such as 0.75 weight percent or less based on the total adhesive weight), or even when the adhesive is free of glass microspheres. It is also achieved in this case.

In some embodiments the cured adhesive exhibits a non-aging lap shear strength of at least 25 MPa, at least 28 MPa, or at least 30 MPa, up to 50 MPa, as measured on test samples prepared as in the Examples below. The lap shear strength after corrosion aging may be at least 16 MPa, at least 17 MPa, at least 18 MPa, or at least 20 MPa.

It is theorized that applying the adhesive of the present invention to a metal substrate improves product performance related to corrosion resistance by in situ cleaning/surface modifying the metal with the phosphate containing additives present in the adhesive.

The cured adhesive forms a strong bond to a variety of substrates. Especially when the adhesive is used as a structural adhesive, the greater the bond strength properties it exhibits, the better it is. Generally, the bond strength properties of the adhesive formulations of the present invention may be greater than 15 MPa up to 50 MPa depending on the type and stiffness of the bonded substrate. In one embodiment, the bond strength properties of the adhesive formulation of the present invention are from about 10 MPa to about 50 MPa, in another embodiment from about 12 MPa to about 45 MPa, and in still another embodiment from about 15 MPa to about 40 MPa. It can be. Advantageously, the bond strength properties of the adhesive formulation containing the PEC additive of the invention are not reduced from the original corrosion resistance properties of the adhesive without the PEC additive. For example, the presence of a phosphorus-containing additive in an amount ranging from about 0.1% to about 0.5% by weight in a formulated adhesive will change the initial adhesive strength of the adhesive compared to an adhesive formulated without the PEC additive of the present invention. I don't order it. In one embodiment, the adhesive strength characteristic of the adhesive is greater than about 34%, in another embodiment greater than about 20% to about 25%, and in a most preferred embodiment greater than about 0% to about 5%. does not decrease

When used as a structural adhesive, it is generally required that the formulations of the present invention bond substrates together without destruction. Advantages of using the formulated adhesives of the present invention include a reduction in the failure mode cycle of the adhesive. Advantageously, the failure mode cycle of the adhesive formulation containing the PEC additive of the invention is reduced from the original failure mode cycle of the adhesive without the PEC additive. For example, the presence of a PEC additive in a formulated adhesive of the present invention reduces the failure mode cycle of the adhesive by less than about 100% in one embodiment and about 40% in another embodiment compared to an adhesive formulated without the PEC additive. % to about 60%, and in still other embodiments from about 90% to about 100%.

In the formulated adhesives of the present invention, the presence of PEC additives in an amount ranging from about 0.1% to about 0.5% by weight increases the initial viscosity of the adhesive (without additives) to a range of about 3% to about 15%, thereby: The initial viscosity of the adhesive can be changed. In a 72 hour measurement of viscosity, the initial viscosity of the formulated adhesive of the present invention can increase by about 30% to about 400%. However, this increase in viscosity does not limit the application of the adhesive of the invention to metal substrates.

The cured adhesive may have an elastic modulus of at least 800 MPa, at least 1,500 MPa, or at least 1,800 MPa. The cured adhesive may exhibit a tensile strength of at least 25 MPa or at least 28 MPa. The cured adhesive may have an elongation at break of at least 2%, at least 4%, or at least 6%, up to 40%, up to 20%, up to 15%, or up to 10%.

As previously mentioned, adding PEC compounds to epoxy-based adhesive polymers increases the corrosion properties of the adhesive formulation. Additionally, the bonding strength of the adhesive remains the same or does not decrease significantly. For example, adding phosphoric acid (0.1% by weight), QM1326 (0.5% by weight) or ^SIPOMER® PAM (0.5% by weight) to BETAMATE 1620 US at low levels increases the corrosion resistance to bonded Al 6111. After 500 hours and 1000 hours corrosion testing, the BETAMATE sample without additives loses almost 90% of its lap shear strength on aluminum. Using the additives of the present invention, the corrosion tested samples show significantly better results (see Table I).

[Table I] Accelerated corrosion test lap shear results

Improved lap shear performance after 500 hours of exposure to accelerated corrosion conditions of 3% NaCl salt spray at 35°C for two metal substrates bonded by an adhesive containing the PEC additive of the present invention shows that the PEC additive and the aluminum substrate and epoxy Due to resin interaction; (1) PEC additives improve the interaction between the active ingredients in the adhesive and the substrate surface by cleaning/etching the metal surface in situ to remove extraneous organic contamination from the metal surface; (2) PEC additives reduce the oxide/hydroxide thickness of the aluminum substrate, increasing the interaction between the active ingredients in the adhesive and the metal substrate surface; (3) the PEC additive improves the interaction between the active ingredients in the adhesive and the substrate surface by creating a coating of an insoluble metal-phosphorus layer ranging in thickness from about 0.1 nanometers (nm) to about 7 nm; (4) The PEC additive chemically reacts with at least a portion of the adhesive formulation containing the epoxy functional groups of the adhesive polymer resin to form an ester bond, which creates a new organic phosphate, which ultimately forms a bond between the components in the adhesive formulation and the substrate surface. It is theorized that it can improve interaction.

Example

The following examples are presented to illustrate the invention in further detail but should not be construed as limiting the scope of the claims. Unless otherwise stated, all parts and percentages are by weight.

Various terms and names used in the examples are explained below.

“PEM” stands for phosphoethyl methacrylate.

“SST” stands for Salt Spray Test.

“Ave” stands for average.

“Stdev” represents standard deviation.

Al6111 contains 0.7 to 1.1% silicon, 0.5 to 1% magnesium, 0.15 to 0.45% manganese, up to 0.4% Fe, up to 0.15 uranium, up to 0.1% chromium, up to 0.1% titanium, and the balance aluminum. It is a certain grade of aluminum metal. Al6111 is available from ACT, Hillsdale, MI.

FERROCOTE ^® 61 AUS is an automotive approved oil-based anti-rust reagent containing mineral oil, sulfonic acid, petroleum, and calcium salts. FERROCOTE 61 AUS is available commercially from Quaker Chemical Corporation.

Alcoa 951 is a vinyl phosphonic acid/phosphinic acid, polyacrylate, available from Arconic.

BETAMATE 1620US is an epoxy structural adhesive based on toughening epoxide chemistry and is available from The Dow Chemical Company. BETAMATE 1620US is based on a toughening technology that uses capped polyurethane prepolymers as primary toughening agents together with conventional toughening agents such as adducts of bisphenol A-based epoxies and carboxyl-terminated butadiene acrylonitrile (CTBN). BETAMATE is a trade name of The Dow Chemical Company. BETAMATE 1620US alone provides good strength and reasonable failure modes on raw aluminum in its initial state, but gives very poor results after corrosion tests such as 500 to 1000 hours salt spray exposure.

In the following examples, three phosphate containing additives were formulated in BETAMATE 1620 US: (1) 85% phosphoric acid; (2) QM1326; and (3) SIPOMER PAM 4000. Additives were formulated into the system on a weight percent basis.

QM1326 is an adhesive product used to improve adhesion to metallic substrates when incorporated into acrylic or styrene-acrylic systems. QM1326 is a mixture of phosphoethyl methacrylate (PEM) monoester, PEM diester, phosphoric acid and methyl methacrylate + monomeric impurities. QM1326 is available from The Dow Chemical Company; It is described generally in U.S. Patent No. 5,191,029, issued to Rohm and Haas in 1993.

SIPOMER PAM 4000 is a phosphoethyl methacrylate polymer and is commercially available from Rhodia Solvay Group. SIPOMER PAM-4000 is a trade name of Rhodia Solvay Group.

D.E.R. 331 is a bisphenol A-based epoxy resin with an EEW of 182 to 192; Available from Olin Corporation.

In the examples below, solutions of different weight percent values of additives were prepared in D.E.R. The storage stability of the additive was evaluated by mixing it with 331 bisphenol A-based epoxy resin. After mixing, the solution was placed in a glass bottle, equilibrated in a water bath at 25° C., and the viscosity was measured from 0.3 to 20 rpm using a Brookfield viscometer model DV-E equipped with a #5 or 7 spindle. The samples were placed in an oven at 43°C for 24 and 72 hours and the viscosity was measured again. The results are provided in Table II. These viscosity values indicate that some of the loadings (e.g. 5 wt% QM1326) were unacceptable for further testing due to the high viscosity values.

Lap shear testing was performed according to ASTM D1002-10 (October 2010). Initial lap shear samples were pulled using a 50 kN load cell on an Instron tensile tester model 5500R. The test speed was 2 inches/minute (50 mm).

The viscosity of the tested adhesive was measured with a viscometer at 25° C. and a shear rate of 3 1/s.

Salt spray testing was performed according to ASTM B117-l6 (April 2016). Salt spray samples were placed in a salt spray cabinet and exposed for 500 hours and 1000 hours according to ASTM B117-16. Conditions were 35 °C and 5% NaCl solution for spraying.

Oxygen detected on the surface of a metal substrate can be determined using SEM/EDS. “SEM/EDS” stands for scanning electron microscopy. The levels of metal elements found in a metal substrate can be recorded by XPS. “XPS” stands for X-ray photoelectron microscopy.

Examples 1 to 10 and Comparative Example A

Prepare a series of mixture samples as described in Table II; The viscosity of the samples was measured according to the viscosity measurement procedure described above. The results of the viscosity measurements are listed in Table II.

[Table II] D.E.R. Viscosity change after adding additives to 331

From the results in Table II, it can be seen that adding too much PEC (e.g., more than about 3% by weight) to the adhesive resin can significantly increase the viscosity (more than 3 times the initial) after 72 hours at 23°C and result in an unstable solution. You can see that it can be created. Therefore, adding too much PEC to the adhesive resin may cause instability in BETAMATE 1620 US containing adhesive resin. When low levels of PEC (e.g., less than about 3 weight percent) are added to the adhesive resin, the mixture appears to be stable. “Stability” herein means an increase in viscosity of less than 100%; Viscosity is measured by a Brookfield viscometer.

Examples 11 to 20 and Comparative Example B

A series of formulated adhesive samples and a series of lap shear samples were prepared as described in Table III. Various PECs were added to BETAMATE 1620 US and tested.

[Table III] Lap shear strength for initial samples with various additive loadings

[Table III] Lap shear strength for initial samples with various additive loadings (continued)

In these examples, an aluminum substrate, untreated Al 6111, was used. Aluminum substrates were supplied precut into 1 inch (25.4 mm) x 4 inch (101.6 mm) strips. The thickness of each metal substrate strip was 1 mm. Al 611 metal was chosen because it is a typical automotive grade metal used in closure panels such as doors and hoods of automobiles. Al 611 metal is also a good differentiator for adhesives.

Lap shear samples were prepared by cleaning the existing mill oil on the surface of the sample with acetone and then applying FERROCOTE 61AUS, a common stamping oil used by original equipment manufacturers (OEMs), to the surface of the sample. The adhesive sample was then applied to the lap shear sample by spreading the adhesive over the joining surfaces of the samples using a spatula. The bonding thickness of the adhesive was controlled to 0.25 mm using solid glass beads. The overlap of the joints was controlled to 0.5 inches (12.5 mm) using joint fixtures. After joining, binder clips were placed on both sides of the joint to secure the joint together. The joint was then placed in an oven set to a temperature of 163°C and the adhesive was cured by heating the joint at 163°C for 20 minutes. Three replicates for each example in Table III were prepared for each condition. Lap shear testing was performed according to ASTM D1002-10.

After cooling the lap shear samples to room temperature (approximately 25 °C), the initial lap shear samples were pulled using a 50 kN load cell on an Instron tensile tester model 5500R. The test speed was 2 inches/minute (50 mm/minute).

From the results in Table III, it was found that when using too high a weight percent PEC to bond Al6111 using BETAMATE 1620 US, the initial lap shear strength was reduced compared to the control. For example, formulation with 3 wt% QM1326 in BETAMATE 1620 US reduces initial lap shear strength by about 35% compared to the control. On the other hand, when an appropriate amount of PEC is added to BETAMATE 1620 US, the initial lap shear is not affected (see Table III). For example, the initial lap shear for the control sample of BETAMATE 1620 US is nearly 16.2 MPa. When an appropriate amount of PEC is added to the adhesive, the lap shear value is about 16.5 to 16.6 MPa.

Examples 21 to 26 and Comparative Sample C and Comparative Sample D

In these examples, according to ASTM B117-16, a series of salt spray samples described in Table IV and Table V were placed in a salt spray cabinet and exposed for 500 hours as described in Table IV and for 1000 hours as described in Table V. I ordered it. The conditions for the salt spray test were 35° C. and 5% NaCl solution for spraying. After removal from the cabinet, the salt spray samples were allowed to equilibrate at ambient conditions for 24 hours prior to testing.

The results of the above tests show that when bonding Al6111 using BETAMATE 1620 US with the optimal amount of PEC and exposed to salt spray (3 wt% NaCl) for 500 hours (see Table IV) and 1000 hours (see Table V), The system containing PEC significantly outperforms the control sample in terms of lap shear. For example, at 500 hours of exposure, the control sample has a lap shear of nearly 0.4 MPa, while systems formulated with various PECs range from about 12 to 13 MPa.

[ Table IV] Lap shear strength for 20-day exposed samples with additives

[ Table V] Lap shear strength for 40-day exposed samples with additives

Analytical tests were performed on various samples of BETAMATE 1620 US and the results of such tests are described with reference to Figures 1-3.

Assay experiment 1

Figure 1 shows test samples of exposed aluminum surfaces after lap shear testing of control samples (left column I) and QM1326 formulated BETAMATE 1620 US samples (right column II) exposed to 1000 hours of salt spray (3% NaCl). A series of images are shown, including two optical images (row A, top) and four electron micrographs (row B, middle and row C, bottom). On the surface of the control sample, dark and light areas can be observed. The bright areas are dominated by Al and O, with O ranging from 5% to 10% by weight, while the dark areas contain the main contributions from Al and O, with O ranging from 25% to 60% by weight. For comparison, a baseline unexposed Al sample can be examined, which may contain approximately 3% O by weight. Therefore, it appears that exposure of the control samples to accelerated corrosion conditions increased the amount of O (presumably aluminum oxide) on the aluminum surface. In comparison, the QM1326 formulated BETAMATE 1620 US system, when exposed to the 1000 hour salt spray test, appears almost similar to samples not exposed to accelerated corrosion conditions, suggesting no major surface modification to the sample. The micrograph in Figure 1 also shows dark and light areas. The bright region contains major contributions of Al and approximately 3% by weight O, consistent with the initial reference aluminum. Dark areas represent areas with predominant levels of C, consistent with the presence of adhesive.

Results from the above experiments indicate that BETAMATE 1620 US control samples after exposure to accelerated corrosion conditions contain increased amounts of oxygen and aluminum oxide at the sample surface, consistent with oxide formation. When inspected using SEM/EDS, the amount of oxygen detected on the surface increased 20-fold. This growth layer delaminates easily and is probably the root cause of poor lap shear performance. In comparison, when the adhesive contains PEC, no signs of accelerated corrosion are observed, as shown in Figure 1.

Assay experiment 2

Figure 2 shows two optical views of a test sample of an aluminum surface after lap shear testing for a pristine (not exposed to accelerated corrosion conditions) control sample (left column I) and a QM1326 formulated BETAMATE 1620 US sample (right column II). A series of images are shown, including an image (row A, top) and four electron micrographs (row B, middle and row C, bottom). Figure 2 shows the surface of a control sample with few features, with some dark areas indicating areas of adhesive. The continuous region contains major contributions from Al and about 3 wt% O, consistent with the reference aluminum sample. In general, micrographs of these and other areas show that the control sample of BETAMATE 1620 US suffered primarily adhesive failure to the substrate. Lower energy micrographs (e.g., 5 keV; not shown) suggest that some residual carbon at the surface of the test sample indicates a lesser degree of cohesive failure or residual stamping oil. In comparison, the BETAMATE 1620 US system formulated with QM1326 contains significantly more carbon area at the surface, consistent with cohesive failure. The images in Figure 2 show that formulating the adhesive with QM1326 changes the failure mode relative to the initial system.

Results from the above experiments show that adding QM1326 to BETAMATE 1620 US changes the failure mode during lap shear testing from a predominantly adhesive failure mode for the control to a predominantly cohesive failure under non-corrosive conditions, as shown in Figure 2. indicates. This suggests an alteration in the interaction between the adhesive and the metal surface. However, this change does not increase the initial adhesive strength.

Assay experiment 3

Figure 3 shows several electron micrographs of the polished surface of an aluminum substrate, Al6111, before (left column I) and after treatment with QM1326 (right column II). Asterisks and arrows are inserted into the image for feature locations. The scale bar in the micrograph is 5 micrometers. Figure 3 shows that adding QM1326 to the adhesive removes residual organic contamination from the metal. This removal of organic contamination can be best visualized by images where delocalized dark areas are found before but not after QM1326 exposure. If the differences observed in the images are due to the interaction of QM1326 with the surface and not due to additional cleaning (cleaning the surface with water and acetone after exposure), the images show that treatment with QM1326 can etch and clean the aluminum. indicates. A second observation from the QM1326 treated aluminum surface is that a series of small dark areas appear on the treated surface after treatment. These small dark areas are best visible in the lower right corner of the image in Figure 3. Similar areas were observed in previously examined samples (not shown), suggesting pitting of the surface, supporting the phenomenon of QM1326 etching the aluminum surface.

Referring to Figure 3, Table VI and Table VII, exposure of Al6111 to various PECs: (i) reduces the aluminum oxide layer thickness (see Table VI), and (ii) creates a thin phosphorus-containing layer on Al. (see Table VII), (iii) remove residual carbon-rich surface material (see Figure 3), and (iv) etch the surface to create small “pits” (see Figure 3). It is believed that this process also occurs when PEC is applied as a component formulated within the adhesive.

[Table VI] XPS weight percent and oxide thickness for aluminized surfaces

[Table VII]

The results of this test also show that Al treated with QM1326 and soaked in 3% NaCl also does not provide a corrosion advantage over the control. Therefore, the improved corrosion resistance appears to be related to the improved adhesive/barrier properties between the metal and 1620US. Moreover, aluminum substrates modified by aggressive solvent cleaning or polishing with sandpaper provide similar benefits to those observed using PEC (see Tables IV and V). This indicates that surface modification plays a significant role in improving corrosion resistance. Additionally, PEC is observed to interact with bisphenol A diglycidyl ether or BADGE through ring opening of the epoxide group forming an ether linkage with the phosphate group. In the case of QM1326 and SIPOMER PAM 4000, this reaction forms a modified epoxy with an ester containing acrylate component. These newly formed organic phosphates may be theorized to play a role in improving corrosion resistance. And, exposing Al6111 to epoxies with PEC additives (e.g., bisphenol A diglycidyl ether) changes the chemical properties of the metal. Specifically, Mg, C, Ca and Na are removed from the metal surface. This strongly supports that PEC can interact with metal surfaces when delivered with an epoxy organic delivery system.

Claims (22)

(I) 40 to 65% by weight of epoxy-based adhesive polymer;
(II) 0.1 to 3% by weight of a phosphorus element-containing compound, which is a mixture of phosphoethyl methacrylate monoester, phosphoethyl methacrylate diester, phosphoric acid, and methyl methacrylate; and
(III) An adhesive composition containing an epoxy curing catalyst. The method of claim 1, wherein the epoxy-based adhesive polymer is (a) a curable epoxy compound or a combination of two or more curable epoxy compounds; (b) at least one reactive urethane group- and/or urea group-containing polymer having at least one polyether and/or diene rubber segment having a weight of at least 1,000 atomic mass units and capped isocyanate groups and having a number average molecular weight of at most 35,000, An adhesive composition comprising (c) at least one epoxy cure catalyst, and (d) a curing agent. The adhesive composition of claim 1, wherein the epoxy-based adhesive polymer is bisphenol A diglycidyl ether. The adhesive composition of claim 1, wherein the epoxy-based adhesive polymer is a urea toughening polymer. The adhesive composition of claim 1, wherein the amount of the epoxy-based adhesive polymer is 40% to 60% by weight. The adhesive composition of claim 1, wherein the composition has a corrosion resistance of 10 megapascals to 13 megapascals. The adhesive composition of claim 1, wherein the composition has a bond strength of 7.1 megapascals to 13 megapascals. (a) 40 to 65% by weight of an epoxy-based adhesive polymer;
(b) 0.1 to 3% by weight of elemental phosphorus-containing compound, which is a mixture of phosphoethyl methacrylate monoester, phosphoethyl methacrylate diester, phosphoric acid, and methyl methacrylate; and
(c) mixing epoxy curing catalyst
A method of producing an adhesive composition comprising a. 0.1 to 3% by weight of elemental phosphorus-containing compound, which is a mixture of phosphoethyl methacrylate monoester, phosphoethyl methacrylate diester, phosphoric acid, and methyl methacrylate, is mixed with 40 to 65% by weight of an epoxy-based adhesive polymer and A method of increasing the corrosion resistance properties of an adhesive composition comprising adding to an epoxy curing catalyst. 10. The method of claim 9, wherein the elemental phosphorus-containing compound additive acts as an in situ surface cleaner to promote improved interaction between the adhesive and the metal surface while also removing surface contamination from the metal surface. . As a method of joining two substrates,
(A)
(a) 40 to 65% by weight of an epoxy-based adhesive polymer;
(b) 0.1 to 3% by weight of elemental phosphorus-containing compound, which is a mixture of phosphoethyl methacrylate monoester, phosphoethyl methacrylate diester, phosphoric acid, and methyl methacrylate; and
(c) mixing the epoxy cure catalyst to form a structural adhesive formulation; and
(B) After contacting the formulation from step (A) with at least a portion of the surface of the first substrate, the first substrate is contacted with another second substrate at the bondline between the two substrates. forming a layer of the adhesive of step (A) to form an assembly;
(C) contacting the first substrate and the second substrate through a layer of the adhesive formulation at the bonding surface between the two substrates to form an assembly; and
(D) curing the adhesive layer at the bonding surface by heating it to a temperature of 130° C. or higher to form a cured adhesive bonded to the two substrates at the bonding surface.
Method, including. 12. The method of claim 11, wherein the first substrate is aluminum. 12. The method of claim 11, wherein the second substrate is a composite material. 12. The method of claim 11, wherein the first substrate is steel and the second substrate is steel. 12. The method of claim 11, wherein the first substrate is steel and the second substrate is aluminum. 12. The method of claim 11, wherein the first substrate is steel and the second substrate is a composite material. 12. The method of claim 11, wherein the first substrate is aluminum and the second substrate is aluminum. 12. The method of claim 11, wherein the first substrate is aluminum and the second substrate is a composite material. 12. The method of claim 11, wherein the adhesive is used for underbonding. delete delete delete